1. Field of the Invention
The invention relates to a membrane switch circuit and a keyswitch using the membrane switch circuit.
2. Description of the Prior Art
A keyboard, which is the most common input device, can be found in variety of electronic equipments, such as household computer, laptop computer, personal digital assistance (PDA), or the like. A membrane keyboard has been widespread because it produces less noise while pressing a membrane keyswitch.
During the procedures of manufacturing a membrane keyboard, a deformable member is adhered to an insulating layer of a membrane switch circuit. The deformable member is deeply affected by air therein while being pressed. If the keyswitch has a vent, the deformable member will move smoothly when the keyswitch is pressed. Accordingly, the user can use the keyboard with great smoothness.
However, it is a critical consideration about where the vent should be disposed. For example, Hu (U.S. Pat. No. 6,191,776) has disclosed a keyswitch structure with a vent. Although the air can be exhausted from the vent, liquids (e.g. water or beverage) may enter the keyboard through the vent since the vent is disposed on a base plate. Consequently, the circuit within the keyboard may be damaged.
Therefore, the invention discloses a membrane switch circuit and keyswitch using such membrane switch circuit to solve the aforesaid problems.